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Liquid scintillator for an off-axis neutrino detector? (The Minnesota group)

Liquid scintillator for an off-axis neutrino detector? (The Minnesota group). We are actively investigating a liquid scintillator option for the off-axis detector Engineering mostly done (for MINOS) Have made prototypes for test, using PVC extrusions and scintillator from MINOS studies

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Liquid scintillator for an off-axis neutrino detector? (The Minnesota group)

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  1. Liquid scintillator for an off-axis neutrino detector?(The Minnesota group) • We are actively investigating a liquid scintillator option for the off-axis detector • Engineering mostly done (for MINOS) • Have made prototypes for test, using PVC extrusions and scintillator from MINOS studies • Investigating all aspects of possible optical (CCD) readout schemes – minimizing costs • We have all the components to make our own inexpensive ICCD camera

  2. The concept • Engineering was done for MINOS • Aging, strength of materials, etc. • Optical connections, manifolds, etc. • Fill method (after installation) • Needs  300,000 cells for 20 kT • Can we make readout for $10/cell? Few meters earth, rock… • Cells of liquid scintillator  3 cm  3 cm in 15 m (?) long multicell PVC extrusions • Every 5th layer is water

  3. Light yields • We achieved best reflectivity of 0.965 at peak emission (425 nm) • Square cell geometry more optimal than MINOS • Expected light yield at 15 m in 3 cm cells: • @15m (=10m) =  0.47 • @ 0.965 refl. =  1.33 • In 3 cm cells =  1.28 • Mirror at end =  1.60 •  40 photons from 15 m 1 mm fiber 3.2 pe average • Data from cosmic ray muons crossing a 2.1 cm  2.8 cm PVC extrusion (off-the-shelf – refl. =0.94) • 7.5 m from photodetector (HPD, 10% qe); BC517L scintillator  2.1 cm thick

  4. A possible (likely?) scheme • Light emerges from fibers at angles < 47o (calculated and measured) making lens coupler possible without excessive light loss • Fresnel lens has diameter 15 cm, focal length 2.5 cm (3 coupled lenses each with f=7.5 cm) • Can get 70% light from WLS at focus for demagnification of ½ - goes down rapidly beyond that

  5. Image intensifier • Cheapest from Litton who make zillions for military – “scientific” IIs from Hamamatsu, Photek, Proxitronic, DEP, etc, cost significantly more • Generally much quicker delivery compared to “scientific” IIs – take from existing production lines • Have bought a Gen-2 (1 MCP) 25 mm diameter (S-20 photocathode, P20 phosphor) - cost was $1990 – should go to $1500 for large quantities • We are currently evaluating this device • Have measured gain of 0.8  104 using light from WLS fiber • Must connect to CCD via tapered fiber-optic for maximal light – phosphor light is isotropic (- taper costs $500 in large quantities!)

  6. CCD • CCD quantum efficiency 50% •  $500 for Kodak KAF-0401E including components for electronic readout with pixel ganging • 6.9 mm  4.6 mm active area (9m pixels)

  7. CCD read-noise • Limiting feature • Read-noise a few e/pixel from external amps, etc (- dark current is negligible in our gated operation) • We have many pixels/fiber (CCD industry aims for best resolution – we need worst. • Solution: • Gang pixels together to make bigger pixels – we have electronics to do this – being assembled now

  8. The future • We are currently evaluating light amplification/transmission through all components • We are assembling CCD electronics • Will have an operating ICCD camera in 1 month - see if we can see signal from MINOS scintillators • Test liquid scintillator configurations • We will study simpler versions – e.g., fibers to manifold block  Fresnel  CCD (no II) • We would like help, ideas…….

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